Rock Island 4-6-2 "Pacific" Type Locomotives

Class Details by Steve Llanso

Class P-28 (Locobase 5349)

Data from a table published in AERJ in July 1904 (reference back to Oct 1902, p 351). Additional data from RI 11 - 1903 Locomotive Classification and Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. See also "Report of Committee on Power ...Descriptions of Standard Types of Locomotives", AERJ, Vol (March 1905), pp. 84-85.

Drury (1993) notes they had inside piston valves. The Rock's Committee on Power offered this class as the model for their standard Pacific design. "For very heavy passenger service on divisions with steep grades this type, with a deep firebox and large amount of heating surface, great steaming capacity, and high tractive effort, may be more generally depended upon than any other type of locomotive."

That may been the intent, but Schenectady's 1905 class (Locobase 5366) enlarged the cylinder volume and increased the tube count by 28

It's not clear if they were ever superheated, but as they were retired in 1935-1936, it seems unlikely.

Class P-31 (Locobase 14466)

These Pacifics were enlargements of the P-32s of 1905 that rolled on taller drivers. The grate and firebox were unchanged as was the tube count in the boiler, but tube length grew by 14 inches (356 mm). Other differences included the adoption of Walschaert's outside radial valve gear and more adhesion weight.

Class P-31 - superheated (Locobase 8354)

Data from RI 1 - 1942 Locomotive Diagrams book supplied in May 2005 by Allen Stanley from his extensive collection.

As delivered in 1909 from Alco's Schenectady works, these engines already were fitted with piston valves and Walschaert valve gear (Locobase 14466). Consequently, the superheating upgrade that started a few years later resembled that of the P-32 (Locobase 8353) except for the greater cylinder volume and the longer flues. Some substituted new cast-steel trailing trucks with 10,198-lb tractive-effort Delta boosters and were redesignated P-33-B. A few retained their 26 sq ft of arch tubes, but others replaced the arch tubes with 58 sq ft of thermic syphons at the cost of two small tubes. Although the overall heating surface gain amounted to 12 sq ft, direct heating surface increased by 32 sq ft. This latter figure is shown in the full specifications.

As with the P-32, P-31 retirements began in 1936 and ended many years later. In the case of the P-31s, the last locomotive was withdrawn in 1953.

Class P-32 (Locobase 5366)

The data comes a table published in AERJ in July 1904 (reference back to Oct 1902, p 351). See also "Pacific Type Passenger Locomotive", American Engineer and Railroad Journal, Vol 79, No 8 (August 1905), pp. 282-283.

A larger version of the P-28, the P-32s had a somewhat more generous tube count. Drury (1993) notes that although they came with outside-bearing trailing trucks, the P-32s retained slide valves on all but four of this class.

Class P-32 - superheated (Locobase 8353)

Data from RI 1 - 1942 Locomotive Diagrams book supplied in May 2005 by Allen Stanley from his extensive collection.

As noted in the earlier version, these were big, saturated-steam locomotives with slide valves. An upgrade to superheating involved a series of changes that were typical of such a transformation. The slide valves were replaced by 12" piston valves and these were actuated by outside Walschaert radial valve gear.

The firebox was untouched (although the 23.6 sq ft of arch tubes added to the firebox heating surface may have been come later), but the boiler was reworked in the usual fashion with dozens of small tubes replaced by the superheater flues. A less usual change was the 1" increase in cylinder diameter.

Retirements from this class stretched over a 14-year period from 1936-1950.

Class P-33 (Locobase 1194)

Data from RI 1 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. Firebox heating surface includes 58 sq ft of syphons. The design was originally supplied with 26 sq ft of arch tubes.

Following on from the P-31 class that arrived the year before (Locobase 8354), this class had larger-diameter fire tubes and was delivered with a superheater already installed. Although 59,500 doesn't seem to be a high Grate Demand Factor, Drury (1993) says that the small grate was overmatched by the 25 x 28 cylinders originally fitted by Alco-Schenectady. These engines soon received the smaller cylinders indicated in the specifications. Some later substituted new cast-steel trailing trucks with 10,198-lb tractive-effort Delta boosters

(Note: the official name of the Rock Island was the Chicago, Rock Island, & Pacific or CRI&P.)

Class P-40 (Locobase 1193)

Data from Railway Age (9 January 1914), revised and supplemented by RI 1 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection Firebox heating surface included 25.4 sq ft of arch tubes.

Improved P-33s (Locobase 1194) by Alco-Brooks that featured a larger grate that allowed restoration of the 25 1/2" x 28" cylinders that had overpowered the smaller grate. American Vandium Facts for March 1914 pointed out that these engines had vanadium cast steel frames, which had been introduced on the Rock Island in 1912.

The 1914 Railway Age published comments by WJ Tollerton, Chief Mechanical Superintendent, who noted that on one run, one of these Pacifics hauled a 12-car, 900-ton train began climbing a 6-mile-long 1% grade at 35 mph and maintained an average speed of 27 mph.

Retirements began in the late 1930s with the last engine leaving in 1952. Unlike earlier Pacifics on the Rock, this class didn't receive trailing truck boosters or thermic syphons.

Class P-46 (Locobase 142)

Data from 1930 Locomotive Cyclopedia table. (Thanks to Chris Hohl for his November 2013 email identifying the valve gear and for pointing out the mixed valve-gear setup, which is described in Alfred Bruce, The Steam Locomotive in America (New York: Bonanza Books, 1952), pp. 201-201, 210.)

Firebox had 106 sq ft (9.85 sq m) of thermic syphons. Compare with L&N #295 (Locobase 149) and MP #6000 (Locobase 152) for very similar dimensions. One engine of a standard Alco three-cylinder design modified slightly for the three different railroads. Bruce's diagram shows that like the other Alco three-cylinder locomotives, all three cylinders were line abreast and roughly equally spaced. But the two right-hand piston valves were closely spaced over the right-hand cylinder and linked together by a solid arm that pivoted around its center, thus actuating first the central valve, then the outside right valve